To get an indication on whether exposure to dioxins and PCBs might cause a problem in countries joining the European Union in 2004, a study of their levels in 16 butter samples from 8 countries (Cyprus, Czech Republic, Estonia, Lithuania, Poland, Romania, Slovenia and Slovakia) was performed. Comprehensive data on accuracy of the applied analytical method were requested. Seven quality control samples had a mean recovery of 97.9 % with a CV of 3.0 % for WHO-PCDD/F-TEQ, eight quality control samples had a mean recovery of 100.4 % for PCB-TEQ with a CV of 3.3 %. All butter samples were run as duplicates resulting in a confidence region of 95 % statistical certainty of 4.6 % for WHO-PCDD/F-TEQ and of 3.5 % for WHO-PCB-TEQ.All samples except one from Romania are in the range of 0.21 to 0.59 pg WHO-PCDD/F-TEQ/g fat (upper bound), all samples except one from Romania and one from Estonia in the range of 0.32 to 0.82 pg WHO-PCB-TEQ/g fat (upper bound) and all samples except one from Romania and one from Estonia in the range of 0.57 to 1.23 pg sum WHO-TEQ/g fat (upper bound). The maximum values were found in samples from Romania (0.98 pg WHO-PCDD/F-TEQ/g fat; 1.75 pg WHO-PCB-TEQ/g fat) and Estonia (0.26 pg WHO-PCDD/F-TEQ/g fat; 1.62 pg WHO-PCB-TEQ/g fat). As a conclusion, all samples except one from Romania and one from Estonia are in the range of the actual low background contamination for PCDD/F and dioxin-like PCBs. The elevated samples are below the EU action and maximum levels. In all samples except one from Estonia, the contribution of dioxin-like PCB to sum WHO-TEQ is in the range from 47 to 68 % which reflects the usual range especially in Europe. In one sample from Estonia this contribution is 86 % which is an indication of a particular PCB source. 38 PCB congeners were determined allowing a detailed discussion of the relative contribution of individual congeners to total PCB concentration.